<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    console.log('typeof(String)='+typeof(String))
    var n1 =111;
    var n2 =5;
    console.log(n1+n2);
    console.log(String(n1)+n2);

    console.log('typeof("aaa")='+typeof("aaa"))//String
    var s1 = new String('123');
    console.log(typeof s1);//object
</script>

</body>
</html>